Hi Greg, welcome to the group! So, you want to be a baldie huh? Cool, a great hairstyle.
I'm BBC too, but no shadow at all with the grey hair. When you get a good shaving routine down, and can shave against the grain, it will minimize the shadow. Getting a nice tan on your head will help, too. I would stay away from any chemicals or hair removal products, I've heard they can burn you skin.
I wouldn't worry about some shadow. I kinda like it on some guys. It shows you are BBC, and you have the guts to shave a full head of hair. Let's see some before and after pictures.